The effectiveness of selection for reduced avian leukosis virus shedding in different chicken strains.

A survey was made of the shedding rates of several generations of two experimental and 13 commercial lines of chickens that have been subjected to avian leukosis virus shedding tests and selective repopulation. Definite progress was made in reducing shedding rates in many of the lines, but some lines responded very poorly. These preliminary data do not reveal why progress was not made in some lines of chickens.